@jscottsmith - I'm not sure about e57, but I think PTS is almost the same as an ASCII point cloud file. If you open it as plain text, is there a header with info like the total number of points followed by one line per point:

x y z R G B

x y z R G B

If you remove the header line(s) and rename .pts to .asc, we should be able to process it. Happy to take a closer look if you send a sample to support@sketchfab.com